Veena Singh

Process Optimization for Biodiesel Production

Biodiesel is an alkyl ester of long chain fatty acids and is considered to leave smaller footprint on the environment. It is produced by transesterification of a fat/oil with a short chain primary alcohol like methanol or ethanol. The three routes to its preparation are: alkali catalyzed, acid catalyzed and lipase-catalyzed transesterification. This review summarizes the key patents filed over the last few decades. The chemistry used in these patents is one of the three routes mentioned above. In few patents, heterogeneous catalysts have been used for catalyzing the transesterification process. The innovations mostly concern fine-tuning of the reaction conditions, plant design to improve logistics and use of glycerol produced as a by-product during biodiesel production. There is a concern that biofuels like biodiesel cut into resources like land meant for food crop production. Life cycle studies also create doubt about there being energy efficient fuels. Judicious choices that would differ with different regions are recommended. For the next few decades till better alternatives like hydrogen become viable, biodiesel would continue to be an important alternative fuel.

Combi-protein coated microcrystals of lipases for production of biodiesel from oil from spent coffee grounds

BackgroundReplacing chemical catalysts with biocatalysts is a widely recognized goal of white biotechnology. For biocatalytic processes requiring low water containing media, enzymes for example commercial preparations of lipases, show low catalytic efficiencies. Some high activity preparations for addressing this concern have been described. Protein coated microcrystals (PCMC) constitute one such preparation. The present work describes a Combi-PCMC for synthesis of biodiesel from the oil extracted from spent coffee grounds.ResultsDifferent lipases were screened for biodiesel synthesis from crude coffee oil out of which Novozym 435 gave the best conversion of 60% in 4 h. Optimization of reaction conditions i.e. % water, temperature and purification of coffee oil further enhanced conversion upto 88% in 24 h. A mixture of Novozym 435 and a cheap commercially available 1,3-specific lipase RMIM (from Mucor miehei) was used in different ratios and 1:1 was found to be the best trade-off between conversion and cost. The commercial preparations then were replaced by a novel biocatalyst design called Combi-Protein coated microcrystals (Combi-PCMC) wherein CAL B and Palatase were co-immobilized with K2SO4 as the core and this performed equivalent to the commercial preparations giving 83% conversion in 48 h.ConclusionCoffee oil extracted from spent coffee grounds could be used for the synthesis of biodiesel by using appropriate commercial preparations of lipases. The expensive commercially immobilized preparations can also be replaced by a simpler and inexpensive immobilization design called combi-PCMC which synergizes the catalytic action of a nonspecific lipase CAL B and a free form of 1,3-specific lipase from Mucor miehei.

Quantitative phase imaging of biological cells using spatially low and temporally high coherent light source.

In this Letter, we demonstrate quantitative phase imaging of biological samples, such as human red blood cells (RBCs) and onion cells using narrow temporal frequency and wide angular frequency spectrum light source. This type of light source was synthesized by the combined effect of spatial, angular, and temporal diversity of speckle reduction technique. The importance of using low spatial and high temporal coherence light source over the broad band and narrow band light source is that it does not require any dispersion compensation mechanism for biological samples. Further, it avoids the formation of speckle or spurious fringes which arises while using narrow band light source.

Multispectral quantitative phase imaging of human red blood cells using inexpensive narrowband multicolor LEDs

We report multispectral phase-shifting interference microscopy for quantitative phase imaging of human red blood cells (RBCs). A wide range of wavelengths are covered by means of using multiple color light emitting diodes (LEDs) with narrow spectral bandwidth ranging from violet to deep red color. The multicolor LED light source was designed and operated sequentially, which works as a multispectral scanning light source. Corresponding to each color LED source, five phase-shifted interferograms were recorded sequentially for the measurement of phase maps, as well as the refractive index of RBCs within the entire visible region. The proposed technique provides information about the effect of wavelengths on the morphology and refractive index of human RBCs. The system does not require expensive multiple color filters or any wavelength scanning mechanism along with broadband light source.

Immobilization of enzymes by bioaffinity layering.

Bioaffinity immobilization exploits the affinity of the enzyme to a macro-(affinity ligand). Such a macro-(affinity ligand) could be a lectin, a water-soluble polymer, or a bioconjugate of a water-soluble polymer and the appropriate affinity ligand. Successive layering of the enzyme and the macro-(affinity ligand) on a matrix allows deposition of a large amount of enzyme activity on a small surface. Illustrative protocols show affinity layering of a pectinase and horseradish peroxidase on Concanavalin A-agarose and Concanavalin A-Sephadex matrices, respectively.

Polarization interferometric digital holographic microscope for quantitative phase imaging and coherent noise reduction

In digital holographic interferometry (DHI), coherent noise degrades accuracy of phase information. We present multi-beam polarization DHI in which two cross polarized interferograms are recorded. Fourier analysis of interferograms reduces coherent noise and increases accuracy.

Quantitative phase imaging using spectrally resolved white light interferometry

A spectrally resolved white light interferometry is demonstrated using a discrete spectrum light sources (i.e., RGB LEDs) and monochrome CCD camera for the multi-color quantitative phase imaging of biological cells without color cross talk.

White light phase shifting interferometry and color fringe analysis for the detection of contaminants in water

We report white light phase shifting interferometry in conjunction with color fringe analysis for the detection of contaminants in water such as Escherichia coli (E.coli), Campylobacter coli and Bacillus cereus. The experimental setup is based on a common path interferometer using Mirau interferometric objective lens. White light interferograms are recorded using a 3-chip color CCD camera based on prism technology. The 3-chip color camera have lesser color cross talk and better spatial resolution in comparison to single chip CCD camera. A piezo-electric transducer (PZT) phase shifter is fixed with the Mirau objective and they are attached with a conventional microscope. Five phase shifted white light interferograms are recorded by the 3-chip color CCD camera and each phase shifted interferogram is decomposed into the red, green and blue constituent colors, thus making three sets of five phase shifted intererograms for three different colors from a single set of white light interferogram. This makes the system less time consuming and have lesser effect due to surrounding environment. Initially 3D phase maps of the bacteria are reconstructed for red, green and blue wavelengths from these interferograms using MATLAB, from these phase maps we determines the refractive index (RI) of the bacteria. Experimental results of 3D shape measurement and RI at multiple wavelengths will be presented. These results might find applications for detection of contaminants in water without using any chemical processing and fluorescent dyes.

Longitudinal spatial coherence gated high-resolution tomography and quantitative phase microscopy of biological cells and tissues with uniform illumination

We report longitudinal spatial coherence (LSC) gated high-resolution tomography and quantitative phase microscopy of biological cells and tissues with uniform illumination using laser as a light source. To accomplish this a pseudo thermal light source was synthesized by passing laser beams through an optical system, which is basically a speckle reduction system with combined effect of spatial, temporal, angular and polarisation diversity. The longitudinal spatial coherence length of such light was significantly reduced by synthesizing a pseudo thermal source with the combined effect of spatial, angular and temporal diversity. This results in a low spatially coherent (i.e., broad angular frequency spectrum) light source with narrow temporal frequency spectrum. Light from such a pseudo thermal light source was passed through an interference microscope with varying magnification, such as, 10X and 50X. The interference microscope was used for full-field OCT imaging of multilayer objects and topography of industrial objects. Experimental results of optical sectioning of multilayer biological objects with high axial-resolution less than 10μm was achieved which is comparable to broadband white light source. The synthesized light source with reduced speckles having uniform illumination on the sample, which can be very useful for fluorescence microscopy as well as quantitative phase microscopy with less phase noise. The present system does not require any dispersion compensation optical system for biological samples as a highly monochromatic light source is used.

Quantitative phase imaging using white light interference microscopy with color fringe analysis: A comparative study of color interferograms recorded by single chip and 3-chip CCD color camera

We demonstrate results for phase maps of biological cells using white-light and multi-spectral interference microscopy. Study on comparison of phase maps reconstructed using 1-CCD and 3- CCD is presented to reduce color cross-talk and improved resolution.